The present invention relates to a packing or wrapping film which is provided with an aluminum foil or the like as an intermediate layer and which is hard to break or tear but to easily be openable. The present invention also relates to a packing bag and a package body manufactured by using such packing film.
In a known art, there is provided a packing bag which is manufactured by heat-sealing a composite film formed by laminating a polyethylene film to a cellophane, paper or the like material, and since such packing bag is easily openable by hands along the heat seal portion without using any cutting means, such bag has been widely used. However, such composite film has low rupture strength and, particularly, has an insufficient moisture-proof property, so that there is a limitation to a content to be sealed in the packing bag manufactured by using such composite film.
In order to eliminate such defect, there has also been provided a laminate film, having improved rupture strength and moisture-proof property, formed by combining different kinds of plastic films. Such plastic laminate film has been widely utilized for manufacturing various packing bags, for example, for a material for a package (pouch or bag) or a material for a tubular package for containing sausage, sweet jellied bean-paste or the like.
It is difficult to open by hands the packing bag formed by using the plastic laminate film as a packing material because the plastic laminate film has a certain tearing strength, and in order to easily open such packing bag, a V-shaped or I-shaped notch is formed to the heat-seal portion of the packing bag.
Furthermore, one prior art example of a packing bag manufactured by using the plastic laminate film is shown in U.S. Pat. No. 3,608,815, in which, in order to open the bag from a bent(or folded) portion of the bag, an opening assisting area is formed to the bent portion by penetrating a pin to this bent portion and the bag is opened by hands at the opening assisting area as opening (cut) starting portion.
Still furthermore, the applicant of the subject application has been proposed a packing bag manufactured by using the plastic laminate film. The bag is formed with a bent(or folded) portion from which the bag is openable. In order to facilitate the opening from the bent portion, a plastic laminate film formed by laminating an oriented plastic film having a coarse surface and a non-oriented plastic film having a flat surface is used so that the coarse surface is positioned at the portion of the bag to be bent to open the bag from this bent portion.
However, the prior art techniques mentioned above provide the following defects or drawbacks.
In a case where the packing bag formed with the notch such as the V-shaped notch to the heat seal portion is manufactured by a packing material working maker and then supplied to a user, the notch forming working to the heat seal portion of the packing bag can be done by the working maker at the packing bag forming process, there is no problem for forming the notch to the heat seal portion. However, in a case where the packing material working maker supplies a packing material in roll form to a user and the manufacturing of the packing bag is performed by the user while filling a content in the bag by using a packing machine, it is difficult for the user side to form the notch to the heat seal portion of the packing bag.
Furthermore for the packing bag formed with the opening assisting area at the bent portion by penetrating a pin, it As not necessary to use a jig such as cutter for opening the bag and the bag can be easily opened by hands. However, the formation of the pin penetration hole degrades water-vapor permeability and oxygen permeability as such packing bag. Accordingly, such packing bag is not usable for packing, for example, such a content as coffee powders, rice crackers or the like which will be easily damaged by the moisture, thus limiting contents to be packed, being disadvantageous.
Still furthermore, with the packing bag formed by the plastic laminate film composed of the oriented plastic film having the coarse surface portion and the non-oriented plastic film having the flat surface in a manner such that the coarse surface portion of the oriented plastic film is covered with the flat surface of the non-oriented plastic film, the water-vapor permeability and the oxygen permeability are hardly degraded as the packing bag, so that there is no limitation of thee content to be sealed therein in a shelf-life time period. However, the packing bag of this type is not sufficient for the specific use as a bag capable of substantially completely shutting off moisture and oxygen or for sealing a retort food.
In a view point of reservation of the inner content, it will be preferred to use a laminate film, which is composed of oriented plastic films and an intermediate aluminum foil disposed between these plastic, films, for the material of the packing bag for reserving the inner content for a long term or containing the retort food. However, the packing bag formed of such plastic laminate film is hard to tear, so that it is often difficult to open the bag from the bent portion thereof.
Taking the above matters into consideration, the applicant of the subject application has provided a packing bag suitable for keeping the inner content in a good condition for a long time or for containing the retort food by using a plastic film material which is composed of an oriented plastic film having a coarse surface portion, a non-oriented plastic film having a flat surface, and an aluminum foil or paper sheet disposed between the oriented and non-oriented plastic films.
The laminate film of this structure has a good openability and a good shelf life property. However, in a view point of the shelf life, it is preferred to dispose the aluminum foil between the oriented plastic films.
Moreover, the packing bag formed from She plastic laminate film material with an aluminum foil or paper sheet being interposed between plastic films has a defect such that a value for commercial product is lowered or degraded because of a fear that when the oriented plastic film having the coarse surface portion and the aluminum foil is laminated by using a binder(or an adhesive), a component of the binder may be intruded into through holes formed to the coarse surface portion and leaks to an outer surface of the oriented plastic film. When the binder leaks on the surface of the plastic laminate film, a guide roller guiding the plastic film may be contaminated with the leaked binder when packing bags are continuously manufactured, and furthermore, when the laminated film of the oriented plastic film and the aluminum foil is rolled, a blocking phenomenon may be caused to the rolled continuous laminated film, providing a troublesome problem.
Furthermore, it is generally difficult to tear, by hands, the bonded portion of the tubular package body in which sausage or the like is sealed as an inner content because such package body is required to have a high tearing strength, and hence, it is required to use a jig such as cutter for opening such package body. In this regard, a package body having a heat seal portion from which the package is easily opened by hands has been proposed.
In a package body formed of a plastic laminate film, it is possible to easily open the package by attaching an opening tape having a fine width to the heat seal surface and drawing the opening tape. However, the attaching of the fine tape to the heat seal surface of the package requires an additional working process, which will result in a complicated manufacturing process and a cost increase.
In view of the defects or drawbacks encountered in the prior art mentioned above, a first object of the present invention is to provide a packing film, which is composed of oriented plastic films laminated on both surfaces of an aluminum foil or paper sheet as an intermediate layer, and further provided with an opening starting portion capable of being easily torn.
A second object of the present invention is to provide a packing film having an oriented plastic film, which is laminated, as a front (or outer) surface layer having a coarse surface portion, on an intermediate layer such as aluminum foil or paper sheet, capable of preventing a binder from leaking through the coarse surface portion even with an opening starting portion being easily torn.
A third object of the present invention is to provide a packing bag having a bent portion manufactured by using the packing film mentioned above and being provided with a good inner content keeping performance and capable of being easily torn from the bent portion.
A fourth object of the present invention is to provide a tubular package body manufactured by using the packing film mentioned above, the package body being provided with an opening starting portion extending in a spiral form formed to a peripheral wall of the tubular package body so as to easily open the body from a portion different from a heat seal portion without making complicated the manufacturing process.
According to the present invention, these and other objects can be achieved by providing the following packing films, packing bags and the package bodies.
In one aspect of the present invention for achieving the above first object, there is provided a packing film comprising:
a first oriented plastic film formed as a first surface layer and provided with a first coarse surface portion;
an aluminum foil or paper sheet formed as a first intermediate layer;
a second oriented plastic film formed as a second intermediate layer and provided with a second coarse surface portion which is to be overlapped with the first coarse portion of the first oriented plastic film when laminated; and
a non-oriented plastic film formed as a second surface layer,
wherein the first oriented film, the aluminum foil or paper sheet, the second oriented plastic film and the non-oriented plastic film are laminated in this order so as to provide a laminated multi-layer structure, and an overlapped area of the first and second coarse surface portions constitutes an area to be opened.
In the usual structure, the oriented plastic films are laminated to both surfaces of the aluminum foil or paper sheet, so that a relatively large tearing force is required for starting the tearing of the packing film. However according to the structure of the above aspect, the first and second coarse surface portions formed to the first and second oriented plastic films are formed to be overlapped with each other, so that the plastic film can be torn with a relatively weak force when torn from the area to be opened.
In another aspect of the present invention for achieving the second object, there is provided a packing film comprising:
an oriented plastic film formed as a first surface layer and provided with a coarse surface portion;
an aluminum foil or paper sheet formed as an intermediate layer; and
a non-oriented plastic film formed as a second surface layer,
wherein the oriented plastic film, the aluminum foil or paper sheet and the non-oriented plastic film are laminated in this order so as to provide a multi-layer structure, and
wherein the coarse surface portion of the oriented plastic film is backed by a thin film layer, the oriented plastic film is laminated to the intermediate layer through a binder layer, and the coarse surface portion constitutes an area to be opened.
Furthermore, there is also provided a packing film comprising:
an oriented plastic film formed as a first surface layer and provided with a coarse surface portion;
an aluminum foil or paper sheet formed as an intermediate layer; and
a non-oriented plastic film formed as a second surface layer,
wherein the oriented plastic film, the aluminum foil or paper sheet and the non-oriented plastic film is laminated in this order so as to provide a multi-layer structure, and
wherein the oriented plastic film is laminated to the intermediate layer through a binder having a large amount of solid components and the coarse surface portion constitutes an area to be opened.
According to the structures of this aspect, the binder is prevented from intruding into the coarse surface portion by backing the coarse surface portion of the oriented plastic film with the thin film layer. In addition, when the oriented plastic film is laminated through the binder having a large amount of solid components, the intrusion of the binder is also prevented without backing.
In a further aspect of the present invention for achieving the third object, there is provided a packing bag which is formed by using the plastic films of the structures mentioned above. The packing bag is formed by bending(or folding) a rectangular packing film into a tubular body, by heat sealing side end portions of the bent packing film as a bonded side portion of the tubular body and by heat sealing both end openings of the tubular body so that the non-oriented plastic film constitutes an inner surface layer when formed as the tubular body of the packing bag with the course surface portion positioned to a bent(or folded) portion of the bag body.
In preferred examples, the second oriented plastic film as the second intermediate layer is formed of a non-polar plastic film material. The second oriented film as the second intermediate layer has one surface facing the first intermediate layer and another surface facing the non-oriented plastic film and the one and another surfaces of the second intermediate layer are subjected to a corona treatment. The non-oriented plastic film forming the inner surface layer has a surface facing the second oriented plastic film, the surface being subjected to a corona treatment.
According to such packing bag, since the bent portion formed as the area to be opened serves as a portion from which the tearing is started, the tearing can be easily done with relatively weak force.
In a still further aspect of the present invention for achieving the fourth object, there is provided a package body formed by bending a rectangular packing film having a predetermined dimension so as to provide a tubular body, heat sealing both side end portions of the bent packing film as a bonded side portion and closing both opening end portions of the tubular body, the packing film having the structure mentioned above, and an area of the course surface portion constitutes an area to be opened, the area to be opened extending in a linear spiral shape on an outer surface of the tubular body.
According to the structure mentioned above, the package body can be easily opened at an optional position of the area to be opened in the spiral shape, and the formation of such spiral opening area can be easily done in comparison with the case of a fine tape being provided along the heat seal portion.
In the preferred structure, the area to be opened is composed of a plurality of linear portions extending obliquely with equal distance therebetween when the packing film is cut into a rectangular shape having a predetermined dimension in a manner such that a crossing point of an upper edge of one linear portion and an inner edge portion of one side end portion to be bonded of the packing film and a crossing point of a lower edge of another linear portion adjacent to the first mentioned one linear portion and an inner edge portion of another side end portion to be bonded of the packing film are positioned on the same horizontal line on the rectangular packing film. Since the opening area extends in continuous spiral line, the package body can be easily opened.
In the above aspects, the coarse surface portions of the oriented plastic films may be provided by forming through holes or forming through holes and non-through holes to the oriented plastic films.